This invention relates to aircraft engine exhaust nozzles and, more particularly, to a linkage having a curved guide portion for adjusting the position of an exhaust nozzle to change the size of an exhaust flow area.
Conventional aircraft engines, such as turbojet engines, typically include a compressor, a combustor and a turbine. Compressed air mixed with fuel in the combustor generates a flow of hot gases. The hot gases flow through the turbine and expand against a plurality of turbine blades. The turbine blades transform the expansion of hot gases into mechanical energy for driving a rotor shaft that in turn drives the compressor. The hot gases exit the engine through an exhaust nozzle to provide thrust to the aircraft.
Conventional exhaust nozzles are adjustable such that the size of the area through which the hot gases flow changes with changing exhaust flow pressure. The size of the exhaust area is proportional to the thrust that the engine produces. During take-off for example, more thrust is desired than during cruising and therefore a larger exhaust area is desirable. Further, the amount of thrust that the engine produces is related to the amount of fuel that the engine combusts. As a result, adjusting the size of the nozzle for take-off and cruising conditions to provide a desired amount of thrust can increase fuel efficiency.
Conventional exhaust nozzle assemblies include a plurality of adjustable flaps that move in response to changing exhaust flow pressures. To maintain stable movement of the flap, the flap typically includes a slot to guide the flap as it moves. A strut having one end fixed to the engine and another end received in the slot allows flap movement along the slot and prevents significant movement in other directions to stabilize the flap. Conventional slots are linear and the strut is received into the slot at an angle to the linear direction.
One disadvantage of conventional exhaust nozzle assemblies lies in the linear shape of the slot. Relative movement between the strut and the slot is conducive to frictional binding, which may result in flap lock-up. In particular, when the strut forms an angle near 90° with the slot, frictional binding may occur. Further, frictional binding may increase when changing a direction of flap movement. Thus, the frictional binding may limit the range of movement of the flap and therefore limit the benefits to the aircraft engine.
Accordingly, there is a need for an exhaust nozzle assembly that allows a greater range of flap movement while minimizing frictional binding. This invention addresses these needs and provides enhanced capabilities while avoiding the shortcomings and drawbacks of the prior art.